A need to adapt injection quantities which are actually injected to setpoint injection quantities which depend on a respective operating state of the internal combustion engine typically results, for example, from temporal changes of properties of the injection valves or injectors.
Thus, in particular, wear phenomena or deposits can lead to injection parameters, such as the actual opening duration or the actual opening degree of the injection valves, and therefore the actual injection quantity changing during the service life of the injection valves.
In order to adhere to the strict emission standards and to make low fuel consumption possible, the injection system of an internal combustion engine has to be capable, however, of injecting a defined fuel quantity exactly over the entire service life of a corresponding injection valve. Nowadays, very high requirements are made of the stability and accuracy of the injection.
It is therefore essential to compensate for the above-described drift of properties of an injection valve during its service life. To this end, it is known to carry out an adaptation of the injection parameters using the crankshaft/engine speed signal. When combustion occurs in the internal combustion engine, an acceleration of the crankshaft of the internal combustion engine occurs. This acceleration can be detected in the speed signal of the internal combustion engine. The actually injected fuel quantity can be determined from this.
Here, the procedure is in detail such that, during a phase (fuel shut-off phase), during which no injection takes place, a test injection pulse is realized and the acceleration, brought about as a result, of the engine speed is determined and is used as an indication for the actually injected fuel quantity. The actuation data of the injector of the internal combustion engine are then corrected on the basis of the determined actually injected fuel quantity.
However, relatively new vehicles have such phases, in which no injection takes place, to a much smaller extent. This means that the corresponding adaptation or correction of the actuation data is slowed down dramatically. The desired emission standards and the desired low fuel consumption can therefore be optimized only insufficiently in this case. The known solutions, in which a single test pulse is used during a fuel shut-off phase, are therefore in need of improvement.